Solving Persistent ESP and ABR Issues on a 2008 MB S550

After many days and weeks of hunting down an ESP issue, initially pointing at faulty ABS wheel speed sensors and an ABR communication issue, I did the hard thing. I tracked all the ABS wiring and found some frayed wires, which I fixed. That resolved weird communication issues, and then I went and replaced all wheel sensors. I also sprayed brake fluid cleaner through the hubs, making sure there was no dirt, and had a chance to inspect the rear tone rings, which looked okay.

However, the ABS light-on problem remained, and I replaced the ABS pump and module attached to it. Then, the car would only intermittently pop up with an ESP error and disappear with no codes when scanning.

So I got a second ABS replacement module, and now the car complains about the traction control not working. No amount of relearning solved it. It’s yet another bad ABS module and maybe a pump.

So, I am replacing the ABS pump for the third…